Switch mechanism for hand-operated electric tools



- R. CRANMORE SWITCH MECHANISM FOR HAND-OPERATED ELECTRIC TOOLS March 15, 1960 2 Sheets-Sheet 1 Filed June 27, 1957 INVENTOR. Rfiberi lI-rnnmmre BY A TTOP/VEYj March 15, 1960 R. CRANMORE 2,928,921

SWITCH MECHANISM FOR HAND-OPERATED ELECTRIC TOOLS Filed June 27, 1957 2 Sheets-Sheet 2 {WWW/MM I INVENTOR. Rd'beri Errnnmmre Uni d. e we swrrc'n MECHANISM FoR HAND-OPERATED ELECTRIC TOOLS Robert Cranmore, Shelburne Falls, Mass., assignor, by

mesne assignments, to Cutler-Hammer, Inc., Milwaukee, Wis, a corporation of Wisconsin Application June 27, 1957, Serial No. 668,375 14 laims; (e1. zoo-#157 The present invention relates to hand-operated electric power tools and switch actuating mechanism therefor.

Power tools and particularly those of the hand-held type are many times provided with hand grips in which is incorporated a trigger controlling operation of the power tool. Thus as the hand grip is grasped to use the tool the trigger may be manually depressed, usually by the users finger, to actuate the power tool; This is very convenient and, in normal operation; the trigger may simply released to stop the power tool drive. However, this releasing action is contrary to a normal reflex reaction, namely a tightening of an operators grip on the handle when something of an unusual or unexpected nature occurs in operating the-tool and causes it to twist or otherwise cause the operator to feel the-tool is perhaps slipping outof his grasp. As' an example the normal reaction of an operator in drilling a hole through a wall or panel is to grip the handlernore tightly when the drill bit binds as in breaking through to the other side. Many times under these'and other circumstancesit is necessary or desirable to stop the drill immediately, if not instantaneously in order to prevent injury to the tool, the work piece, or, in the case of the more powerful tools, injury to the operator.

The overall object of the invention is to utilize the above-mentioned reflex action to stop operation or, a power tool under circumstances where action of the tool causes a natural increase in the operatorsgrip.

In furtherance of-this end,- it is an object of the inven: tion to provide improved actuating means for an electrical switch, which actuating means include a manually depressible trigger for moving said switch to its'on position upon partial depression thereof and to causethe switch to move to its 01f position upon further de-' pression of the trigger.

The above and other related objects as well as the various features of the invention will be apparent from the following description of the disclosure found in the accompanying drawings and the particular novelty thereof pointed out in the appendedclaims.

In the drawings;

Fig. 1 is an illustration of one type of power tool which may embody the present invention;

Fig. 2 is a greatly enlarged view withvar'ious parts cut away of the switch actuating mechanism indicated in Fig. l with the trigger in its undepressed oif position;

Fig. 3 is a view similar to Fig. 2 with the trigger in a partially depressed on position;

- Fig. 4 is a view similar to Fig. 2' with the trigger in a fully depressed ofi position;- 7

Fig. 5 is a section takenon line" V V of Fig. 2 and looking in the direction ofthe'arr'ows; v

Fig; 6 is a section taken on line VI VI'in Fig; 2 and looking in the direction of the arrows;

Fig. 7 is a-view'similar to Fig. Z-sho'winga modified form of the invention;-

Fig. 9 is a view similar to Fig. 4 showing the relation of parts of the embodiment of Fig. 7.

The hand drill or power tool 16 seen in Fig. 1 is illustrative of one type of power tool in which the present invention may advantageously be embodied. This is par-i ticularly true since the hand drill 16 is of the more powerful type, commonly referred to as a half-inch drill, which can easily become damaged or cause injury to the user if mishandled when in operation. Said drill com: prises a motor housing 18with a powered chuck 20 atits lower end, with hand grips 22, .24 respectively provided at either side of the housing 18. Within the hand grip; Zd'is a switch (not seen in Fig. 1) for actuating the drill- 16in response to partial depression of a trigger 26. The switch actuating means, described in detail below, are arranged to return said switch to its offf position upon further depression of the trigger 26 as might be causedby the reflex action of the drill operator when he grasps the handle 24'tighter upon the occurrence of some mishap. n When operation ofthe drill 16 is stopped in this man; nor, the switch actuating mechanism is so arranged that the trigger 26 may be released and will assume its unf depressed position without reactuating the drill. Also operation of the drill may be stopped in a conventional manner simply by releasing the trigger from said opera tiv'e, partially depressed position. Thus itis not neces sary to establish new habit patterns in using thedrill 7 Switch actuating means for accomplishing these ends are best understood from Figs. 2, 5 and 6'. The switch; partially indicated at 28 (Fig. 2) and the actuating mechanism may be carried by a stationary bracket 30 which isinounted on an extension; arm 32 secured thereto by rivets 33. Extension 32 is fixed by a flange 35 ton surf ace"3'4 formed interiorly of and in part defining the forward wall of a cavity within the hand grip 24. The bracket 3% is generally U-shaped and provided with a depending U-shaped enlargement 36 at itsleft hand end (Fig. 2) which carries a pin 38 forpivotal mounting of the trigger 26. The trigger 26 also'is of a U-shaped configuration with its arms embracing vthe:bracket.. en largement 36 (Fig.5). At the upper end of trigger 26;:a

pin ittspans the arms of said trigger andcarries inpivotal fashion the depending ears of a latch 42. This latch at its other end extends into an opening 44 formed'ina U-shaped switch actuator member 46 which is slidably mounted within the bracket 30. A spring" 48 extends between anupturned tail 50 of said latch and the flange 32 to releasably maintain this connection between the trig ger 26 and the switch member 4-6. I I

The switch member 46 may be arrangedin anyofa number of ways to open and close contacts within the switch 33. What is herein indicated, though not shown in detail, is a conventional toggle type switch. The switch contacts are open when the member 46 is in" its right hand position seen in Fig. 2, and closed in response to movement of-the member 46 to its left hand position seen in Fig. 3. When the switch contacts are open the drill 16 is inoperative and thus the condition illustrated iii Fig. 2 represents the olf position of the member Conversely, since the drill is actuated upon closing-rue contacts on movement of the member 46 to the position of Fig. 3, the on position is shown by Fig. 3 4 it will be seen that switch member 46' is provided a downwardly bent portion 52' (Figs. 2, 3, and 5). A ten; sion spring 54 extends between this portion 52 and v ei stationary bracket 30 to yieldingly maintain member 4'6 in its off position. It will also be noted that the coinbi'ned efieot of springs 48 and 5'4 is, to maintain the? trigger 26' in the undepressed position illustratedin FigQZ Meansare also provided for maintaining the m'efm 46in its-on position for continuous operation. of the drill 16 without manual depression of the trigger. A pin 56 (Fig. 5) is slidably mounted in the bracket enlargement 36 and passes through an elongated opening 58 (see also Fig. 4) in the trigger 26. A spring 60 holds the pin 56 in its inoperative position by engaging the inner surface of a hollow button 62 on the outer end of the pin 56. This button is also seen in Fig. l where it projects from the handle 24 and may readily be depressed by the operator once the drill is in operation. When so depressed the pin 56 enters an opening 64 on the other side of the trigger 26 and thus maintains the trigger in the position shown in Fig. 3, with the switch member 46 in its on position.

f From the above it will be clear that upon the trigger 26 being moved from its undepressed position (Fig. 2) to the partially depressed position of Fig. 3, the switch member 46 will move from its off to its on position and the drill 16 may thereby be actuated.

However, if the trigger 26 is further depressed, as illustrated in Fig. 4, an upper edge of said trigger engages an overlying lateral projection 66 (Fig. 6) extending from the latch 42. The latch pivots at 40 and its outer end is lifted clear of the opening 44. Spring 54 then returns switch member 46 to its ofi position. Thereafter, trigger 26 may be released as desired and will be returned to its undepressed position (Fig. l) by spring 48. Spring 48 will simultaneously cause latch 42 to shift relative to member 46, and re-enter opening 44. The parts will thereupon assume the position of Fig. 1 so that upon partial depression of trigger 26 the drill 16 will again be actuated.

It should also be noted that when pin 56 is depressed to enter opening 64 for continuous operation without manually holding the trigger, the operation of the drill 16 may be stopped by the above-described further depressive movement of trigger 26. This is due, to the fact that opening 64 is of suflicient size to allow such movement and permit spring 60 to return pin 56 to inactive condition. Thus the trigger 26 may be returned to its undepressed position. V The modified form of switch actuating means seen in Figs. 7, 8 and 9 comprises the various elements previously described (and identified by like reference characters) except for a modified form of latch 42'. Latch 42' is formed with a bump or projection 68 beneath spring 48 which is in overlying position. The action of this form of the invention in moving the trigger to its intermediate position and the switch member 46 to its on position (Fig. 8) is identical with that of the switch actuating means previously described.

The bump 68, on latch 42', provides the means for increasing resistance to further movement of trigger 26 to its fully depressed condition which will then release switch member 46 to its off position. As in Fig. 8 the intermediate on position of trigger 26 brings the top edge of the trigger under projection 66 of member 42'. It will be seen also that in order to eflect a lifting or releasing movement of the latch 42', an increased depressive forceon the trigger 26 is required to also transversely deflect spring 48. This provides a feel in the use of the drill 16 which prevents the trigger from inad vertently being depressed beyond its drill actuating position. It is, of course, apparent that other means could be provided to increase the force necessary to lift latch 42 from opening 44 so that trigger 26 would not be inadvertently carried beyond the position of Fig. 8 while continued drill operation was desired.

Having thus described my invention, what I claim as novel and desire to be secured by Letters Patent of the United States is:

l. Actuating mechanism for an electric switch, said mechanism comprising a depressible trigger member, means maintaining said switch in an off position in undepressed, position of said trigger, means responsive to partial depressive movement of said trigger :tpr moving said switch to an on" position, means responsive to further depressive movement of said trigger for returning said switch to its 05 position, yieldable means opposing said depressive movement and returning said trigger to its undepressed position when released, means for maintaining said trigger in said partially depressed position with the switch in its on position, said means for maintaining said trigger in said partially depressed position permitting said further depressive movement to provide for return of said switch to its off position, and spring means rendering said means for maintaining said trigger inoperative in response to said further depressive movement thereby permitting return of said trigger to its undepressed position.

2. Actuating mechanism for an electric switch having a member movable between an on position and an off position and spring means for normally maintaining said member in its off position; apivotally mounted depressibletrigger, releasable means interconnecting said trigger and said member and arranged to move said member to an on position when the trigger is partially depressed, means operative in response to depressive movement of the trigger beyond a partially depressed position for disengaging said interconnecting means whereby said member is returned to its ofi position by said spring means, and other spring means for returning the trigger to its underpressed position and causing reengagement of said interconnecting means between the trigger and theswitch member.

3. Actuating mechanism as in claim l wherein yieldable means are provided to prevent free depressive movement of the trigger beyond said partially depressed position whereby additional pressure is required on said trigger to release said interconnecting means to return said member to its 0E position.

4. Actuating mechanism as in claim 1 wherein means are provided for maintaining said trigger in its partially depressed position with said switch member in its 011" position and wherein said maintaining means permit said further depressive movement and the consequent release of the interconnecting means, and wherein spring means render said maintaining means "inoperative in response to said further depressive movement thus permitting return of said trigger to its undepressed position.

5. Actuating mechanism for an electric switch having a member movable between an on position and an off position and spring means for normally maintaining said member in its .0 position; a pivotally mounted depressible trigger, a latch pivotally mounted on said trigger about an axis parallel to and eccentrically of the axis for mounting said trigger, said latch engaging a catch on said member to provide a releasable connection be tween said trigger and said member and arranged such that partial depressive movement of the trigger will cause said member to move to its on position, said latch having a projection which extends into the path of travel of said trigger and is engaged thereby upon further de pressive movement of the said trigger whereupon the latch will be'disengaged from said member and the member returned to its off position by said spring means, other spring means for returning the trigger to its undepressed position and recngaging said latch with said catch of said switch member, whereby said switch member may again be moved to its on position when the trigger is again partiallydepressed.

6. Actuating mechanism as in claim 5 wherein yieldable means resist engagement of the trigger with the latch projection whereby additional pressure is required on said trigger to disengage said latch from said switch member.

7. Actuating mechanism as in claim 6 wherein the resisting means comprise the said other spring, means for disposing said other spring means in overlying relation with respect to said latch and a second projection from said latch, said second projection being disposed to transversely flex said other spring means upon depressive movement of the trigger beyond said partial depressed position.

8. Actuating mechanism as in claim 6 wherein the trigger is provided with an aperture and a spring opposed slidable pin is arranged to engage an inner edge of said aperture and maintain said trigger in said partially depressed position, said aperture being of suificient size to permit further depression of said trigger to release said latch from said switch member.

9. In an electric switch, in combination, a depressible trigger member, means for normally maintaining the switch in a first position when said trigger member is in its normal undepressed position, means responsive to depressive movement of said trigger member to a stopping position for actuating the switch to another position, and means responsive to further depressive movement of said trigger member beyond said stopping position for returning said switch from said other position to said first position comprising means normally latching said trigger member to said maintaining means for movement in unison when said trigger member is depressed to its stopping position, and means for releasing said latching means in response to said further depressive movement of said trigger member to permit said maintaining means to return said switch to said first position.

10. Actuating mechanism for an electric switch, said mechanism comprising a depressible trigger, means maintaining said switch in an cit position in undepressed position of said trigger, means responsive to a first step of depressive movement of said trigger for moving said switch to an on position, means responsive to further depressive movement of said trigger for returning said switch to its 01f position comprising means for resisting said further depressive movement of said trigger thus requiring substantially greater force therefor than was required for said first step of depressive movement thereby to facilitate maintenance of said switch in its on position if desired, and yieldable means opposing said depressive movements and operative to return said trigger to its undepressed position when released.

11. In a motor operated power tool having a hand grip, a pivotally mounted switch trigger disposed in and extending from said hand grip, said switch trigger being positioned for engagement with the operators hand, means responsive to manually pivoting said switch trigger to an intermediate position to actuate said power tool, means efiective at said intermediate position providing an irregularity in the force required to pivot said switch trigger further thereby affording a definite feel to the operator, means operative in response to further pivotal movement of said trigger beyond said intermediate position to stop operation of said power tool, said means providing an irregularity inthe force being operative to resist said further pivotal movement of said trigger thereby requiring unusual manual force on said trigger to stop operation of said power tool, and means effective upon manual release of the hand grip to return said trigger from its further pivotal position to its normal position without actuating the power tool.

12. A motor operated power tool having a hand grip, a pivotally mounted switch trigger disposed in and extending from said hand grip, said switch trigger being positioned for engagement wth the operators hands, said switch trigger further being manually depressible to an intermediate position to actuate said power tool, said intermediate position providing an irregularity in the depressive force required to move said trigger aifording a definite feel to the operator, means operative in response to further depressive movement of said trigger beyond said intermediate position for stopping operation of said power tool, and means resisting said further depressive movement of said trigger thus requiring unusual manual force on the hand grip to so move said trigger.

13. In an electric switch, in combination, a pivotally mounted depressible trigger member, means for normally maintaining the switch in a first position when saidtrigger member is in its normal undepressed position, means responsive to depressive movement of said trigger member to a stopping position for actuating the switch to another position, and means responsive to further depressive movement of said trigger member beyond said stopping position for returning the switch from said other position to said first position, said maintaining means being responsive to release of said trigger member in said stopping position for returning the switch to said first position and for returning said trigger member to its normal undepressed position.

14. In an electric switch, in combination, a depressible trigger member for operating a switch, means normally maintaining the switch in a first position when said trigger member is in its normal undepressed position, means responsive to depressive movement of said trigger member to a stopping position for actuating the switch to another position, means responsive to further depressive movement of said trigger member beyond said stopping position to return the switch from said other position to said first position, means resisting said further depressive movement of said trigger member thus requiring much greater force to move said trigger beyond said stopping position, and means responsive to release of said trigger member following said further depressive movement thereof and said return of the switch to said first position to cause return of said trigger member to its normal undepressed position without reactuating the switch.

References Cited in the file of this patent UNITED STATES PATENTS 2,586,056 Kling et al. "Feb. 19, 1952 2,616,009 Roeser Oct. 28, 1952 2,630,499 Weld Mar. 3, 1953 2,711,461 Happe June 21, 1955 UNITED STATES" PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2 928 92l March 15, 1960 Robert (Zranmor It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

i In the grant, line 3 and in the heading to the printed specification, line 64 for "a corporation of Wisconsin" each occurrence read a corporation of Delaware Signed and sealed this 30th day' of August 1960.

(SEAL) Attest:

ERNEST w SWIDER ROBERT WATSON Attesting Offier Commissioner of Patents 

